Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$213.92	7.357%	$229.6581	$229.66	$229.65	$229.70
Purchase #2	$95.77	5.424%	$100.9646	$100.96	$100.95	$101.00
Purchase #3	$128.50	11.524%	$143.3083	$143.31	$143.30	$143.30
Purchase #4	$45.87	8.222%	$49.6414	$49.64	$49.65	$49.60
Purchase #5	$71.38	3.592%	$73.944	$73.94	$73.95	$73.90
Purchase #6	$40.41	13.631%	$45.9183	$45.92	$45.90	$45.90
Purchase #7	$105.72	13.542%	$120.0366	$120.04	$120.05	$120.00
7 purchase totals =	$701.57		$763.4713	$763.47	$763.45	$763.40